1. Field of the Invention
This invention relates to a method of biochemical analysis in which a sample liquid such as blood, urine or the like is deposited (or spotted) on a "dry-to-the-touch" chemical analysis film having thereon a reagent layer whose optical density changes by chemical reaction with a specific biochemical component contained in the sample liquid, the chemical analysis film deposited with the sample liquid is incubated at a constant temperature in an incubator and the concentration of the specific biochemical component in the sample liquid is determined by measuring the optical density of the chemical analysis film, and more particularly to a method of dealing with interfering substances which can be generated during incubation of one chemical analysis film and can adversely affect the accuracy of measurement on another chemical analysis film incubated after said one chemical analysis film.
2. Description of the Prior Art
There has been put into practice a dry chemical analysis film with which a specific component such as urea nitrogen, glucose, hemoglobin, ammonia or the like contained in a sample liquid such as blood, urine or the like can be quantitatively analyzed through a droplet of the sample liquid deposited on the film. When biochemical components or the like contained in a sample liquid is analyzed using such a dry chemical analysis film, a droplet of the sample liquid is deposited on the film and is held at a predetermined constant temperature for a predetermined time in an incubator so that coloring reaction (coloring matter forming reaction) occurs, and the optical density of the color formed by the coloring reaction is optically measured. That is, measuring light containing a wavelength which is pre-selected according to the combination of the component to be analyzed (an analyte; sometimes referred to as "a measuring item") and the reagent contained in the reagent layer of the film is projected onto the film and the optical density of the slide is measured. Then the component to be analyzed is quantitatively analyzed on the basis of the optical density using a standard curve (or a calibration curve) which represents the relation between the concentration (or the activity) of the biochemical component and the optical density.
The dry chemical analysis film generally comprises a base film of plastic or the like and a reagent layer formed thereon and is sometimes called a multi-layered analysis element. Further the dry chemical analysis film may comprise a porous material layer such as filter paper impregnated with a reagent. The chemical analysis film is generally used in the form of a slide where the chemical analysis film is mounted in a plastic frame though it is sometimes used without frame. In this specification, the term "chemical analysis film" should be interpreted to include both the chemical analysis slide and the frameless chemical analysis film. The chemical analysis films are transferred to the incubator one by one after deposition of the sample liquid and inserted into cells in the incubator. Each cell is in the form of a slit which opens in the side surface of the incubator, and each chemical analysis film is incubated in the cell and the optical density of the color formed by the coloring reaction is optically measured with the chemical analysis film held in the cell.
As described above, the chemical components to be analyzed with the chemical analysis film include various components such as urea nitrogen, glucose, hemoglobin, ammonia and the like, and different types of chemical analysis film are used for different chemical components.
Depending on the kind of chemical component, gas generated from one chemical analysis film can adversely affect measurement on the chemical analysis film subsequently inserted into the cell when it is inserted immediately after the preceding chemical analysis film is discharged from the cell. For example, when one chemical analysis film is for urea nitrogen and the next chemical analysis film is for ammonia, ammonia gas generated from the chemical analysis film for urea nitrogen remains in the cell and affects the result of measurement on the next chemical analysis film for ammonia.
In order to overcome such a problem, it has been proposed to insert the next chemical analysis slide a predetermined time (about 1 to about 30 seconds) after discharge of the preceding chemical analysis slide. (European Patent Publication No. 365006)
In the system disclosed in Japanese Unexamined Patent Publication No. 2(1990)-247563, a plurality of chemical analysis films for the same analyte are connected to a tape in a continuous length, and the interfering substances are variously dealt with during measurement on one chemical analysis film or between discharge of one chemical analysis film from the cell and insertion of the next chemical analysis film into the cell.
However, the method disclosed in European Patent Publication No. 365006 is disadvantageous in that a predetermined time interval is required between the measurements, which prevents shortening of the time required for the biochemical analysis.
In Japanese Unexamined Patent Publication No. 2(1990)-247563, there is neither description nor suggestion on the case where the chemical analysis film which generates the interfering substances and that affected by the interfering substances are for different analytes. Further though the chemical analysis film in a continuous length is easy to manufacture, it makes it difficult to miniaturize the analysis apparatus. The present invention is directed to a system in which discrete chemical analysis films (those in the form of a slide with frame or in the form of a chip) are used.